The present invention relates to the presentation of map information on a display screen of a computing device, and more particularly, the present invention relates to a way to improve the presentation of map information on a display screen of a computing device when a user zooms in or out.
There are various computing platforms that graphically display maps of geographic areas. For example, some in-vehicle navigation systems include a display screen upon which a map of a geographic area can be displayed graphically. In addition, by using appropriate software applications, maps can also be displayed on general purpose computing platforms, such as personal computers and personal digital assistants.
Some computing platforms and applications that display maps graphically include features that allow a user to interact with the map. Various types of user interaction may be supported. Among the features that may be supported is the ability to zoom in or out. When a user zooms in on a map, a sub-portion of the originally displayed map is selected. The user may operate a pointing device for this purpose. Then, a new map is graphically displayed. The new map corresponds to the geographic area of the selected sub-portion of the originally displayed map. The new map is at a larger scale than the originally displayed map so that new map fills the same area on the display screen of the computing device on which the originally displayed map had been shown.
When a user zooms out on a graphically displayed map, the new map is at a smaller scale that the previously displayed map. The new map corresponds to a geographic area that is larger than the geographic area that corresponds to the previously displayed map such that the geographic area that corresponds to the previously displayed map is only a sub-portion of the geographic area that corresponds to the new map.
Maps shown at different scales on display screens may include different levels of detail. This is done in order to make it easier for a user to read and understand the information presented on the map. For example, large-scale maps may include more detail (e.g., all the streets and other cartographic features may be displayed) whereas small-scale maps may include less detail (e.g., secondary streets and minor features may be omitted). If secondary streets and minor features were not omitted on a small-scale map, the display would contain so much information that a user may find it difficult to understand.
Because maps at different scales are associated with different levels of detail, a lower level layer of map information may become visible or disappear when a user is zooming in and out on a map. The sudden appearance or disappearance of an entire level of map information may sometimes be confusing to the user. In addition, geographic features may be represented differently at different levels of detail. For example, on a large scale map (i.e., a map with a high level of detail), a road on which the lanes are separated by a median may be represented by two separate linesxe2x80x94one line representing the lanes on one side of the median and the other line representing the lanes on the other side of the median. However, on a small scale map (i.e., a map with a low level of detail), a road on which the lanes are separated by median may be represented by only a single line. This change in the appearance of represented features that occurs when zooming in and out on a map can also be confusing to a user. For example, if an area or intersection changes shape significantly when the scale is changed, the user may lose his/her point of reference on the map, i.e., he/she may become unsure where on the map it was that he/she was viewing. This can lead to repeated zooms in and then out while the user tries to determine which roads and features remain the same across the transition between levels of detail.
Accordingly, there is a need for an improved way to represent map features when zooming in and out.
To address these and other objectives, the present invention comprises a method for representing geographic features when a map display is zoomed in or out. The method includes displaying a starting image that shows geographic features at a first scale with a first level of detail and then displaying an ending image that shows the same geographic features at a second scale with a second level of detail. Between the displaying of the starting image and the displaying of the ending image, at least one intermediate image is displayed. The intermediate image combines two component images of at least some of the same geographic features shown in the starting or ending image. The two component images in the intermediate image are at the same scale and are registered with respect to each other so that the same geographic features represented in the two component images coincide. One of the two component images in the intermediate image includes at least a portion of the starting image and is formed using data from a first layer of a geographic database. The other of the two component images in the intermediate image is formed using data from a second layer of the geographic database.